Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur–lithium exchange

• Andreas Unsinn,
• Cora Dunst and
• Paul Knochel

Beilstein J. Org. Chem. 2012, 8, 2202–2206, doi:10.3762/bjoc.8.248

• 9 in 77% yield. Direct Pd-catalyzed Negishi cross-coupling [24][25][26][27][28] of 9 with an arylzinc derivative failed. However, the bromide 9 could be readily converted to the corresponding iodide 10 by a bromine–magnesium exchange using iPrMgCl·LiCl [29][30][31][32][33][34][35] followed by

• iodolysis leading to the iodide 10 in 93% yield. Treatment of 1,2-dibromobenzene with iPrMgCl·LiCl at −15 °C for 2 h followed by a transmetalation with ZnCl2 gives the required zinc reagent 11, which undergoes a Negishi cross-coupling with the iodide 10 at 50 °C (5 h) leading to the alkynyl thioether 1a in

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• the ring-close oxazole, a trend that is evidenced by 1H NMR spectroscopy and attributed to the strong covalent carbon–zinc bond along with the zinc’s low oxophilicity, and this thus allows subsequent palladium-catalyzed Negishi cross-coupling [31][32][33]. This first, highly efficient, stoichiometric

• dehydrogenative couplings of (benz)oxazoles with (hetero)arenes have been developed. Stoichiometric and catalytic direct (hetero)arylation of arenes. Stille and Negishi cross-coupling methodologies in oxazole series [28][30][31][33][34]. Stoichiometric direct (hetero)arylation of (benz)oxazole with magnesate

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• obtained in 63% yield. Also, the dibromothiazole 19 allows insertion of zinc only into the most labile C–Br bond (in position 2) leading to the zincated thiazole 20. After Negishi cross-coupling [10][11][12], the 2-arylated thiazole 21 is obtained in 85% yield. Polar functional groups, such as a tosyloxy

• is obtained in 75% yield. Coumarine (46) can be directed zincated leading to the zinc reagent 47. After a Negishi cross-coupling with an aromatic iodide, the substituted coumarine 48 is obtained in 83% yield (Scheme 8 and Supporting Information File 1, Procedure 3) [28]. This procedure tolerates most

• iPrMgCl·LiCl (64) at −40 °C for 1 h leading to an intermediate magnesium reagent, which after transmetalation to the corresponding zinc reagent using ZnBr2 provides, after Negishi cross-coupling reaction with the bromoquinoline 80, the polyfunctinal triazene 81 in 75% yield. The conversion of the triazene